Physiology and Pathophysiology of Pain Flashcards
what is pain?
unpleasant sensory and emotional experience which we primarily associate with tissue damage or describe in terms of such damage or both
what is nociception?
The detection of tissue damage by specialized
transducers connected to A-delta and C fibers
what do nociceptors respond to?
thermal, chemical, mechanical noxious stimuli
what are the characteristics of A alpha and A beta fibres?
myelinated
large diameter
proprioception, light touch
what are the characteristics of A delta fibres?
lightly myelinated
medium diameter
nocioception
what are the characteristics of the C fibres?
unmyelinated
small diameter
innocouous temperature, itch
nociception
which fibres conduct pain?
A delta and C fibres
what is the spinothalamic tract?
major tract sending impulses to thalamus
where are the cell bodies from the spinothalamic tract located?
Rexed lamina 1, 2, & 5
what are the different types of spinothalamic tracts?
Lateral and ventral or neo and paleo STT
where does the lateral STT terminate?
ventroposterior thalamic nuclei
where does the ventroposterior thalamic nuclei primarily feed into?
somatosensory cortex to facilitate the spatial, temporal and intensity discrimination of painful stimuli.
where does the medial thalamic nuclei recieves input from?
ventral spinothalamic tract
what is the ‘second relay station’
thalamus
what are the connections of the thalamus?
Cortex
Limbic system
Brainstem
where does pain perception occur?
in somatosensory cortex
what is hyperalgesia?
Increased perception of pain or even perception of non-noxious stimuli as noxious stimuli
when does hyperalgesia happen?
whenever there is tissue injury and inflammation
what is primary hyperalgesia?
is hyperalgesia at the site of injury
what is secondary hyperalgesia?
hyperalgesia in the surrounding uninjured tissue
what changes in nociceptor does allodynia cause?
decreased threshold for response
what changes in nociceptor does hyperalgesia cause?
exaggerated response to normal and supranormal stimuli
what changes in nociceptor does spontaneous pain cause?
spontaneous activity in nerve fibres
what is central sensitisation?
It is the response of second order neurons in the CNS to normal input both noxious & non-noxious
what are the 3 main concepts of central sensitisation?
wind-up
classical
long-term potentiation
what does the wind up involve?
Involves only activated synapses
Homosynaptic activity dependent progressive increase in response of the neurons
Manifests over the course of stimuli & terminates with stimuli
what does the classical involve?
Involves opening up of new synapses (silent nociceptors)
Heterosynaptic activity dependent plasticity
Immediate onset with appropriate stimuli
Outlast the initial stimuli duration
Can be maintained even at low levels of ongoing stimuli
what does the long term potentiation involve?
Involves mainly the activated synapses
Occurs primarily for
very intense stimuli
what are the differences in acute and chronic pain?
acute pain- physiological prescense of noxious stimuli serves protective function usually nociceptive
chronic pain- pathologival prescence of noxious stimuli is not necessary does not serve any purpose nociceptive, neuropathic or mixed
what is nociceptive pain?
A sensory experience that occurs when specific peripheral sensory neurones (nociceptors) respond to noxious stimuli
when does nociceptive pain resolve?
when damaged tissue heals (bone fractures, burns)
what is neuropathic pain?
Pain initiated or caused by a primary lesion or dysfunction in the somato-sensory nervous system
is neuropathic pain usually acute or chronic?
almost always chronic condition
does neuropathic pain respond well to analgesics?
no
what increases the transduction in pain?
NSAIDs
Ice
Rest
LA blocks
what increases the transmission in pain?
Nerve blocks
Drugs
Opioids
Anticonvulsants
Surgery
DREZ
Cordotomywhat improves the perception in pain?
Education Cognitive behavioural therapy Distraction Relaxation Graded motor imagery Mirror box therapy
what improves the descending modulation?
Placebos
Drugs
Opioids
Antidepressants
Surgery
Spinal cord stimulation
